Enum describing possible field mask errors.

[Proto definition ![GitHub](https://developers.google.com/site-assets/logo-github.svg)](https://github.com/googleapis/googleapis/blob/master/google/ads/googleads/v26/errors/field_mask_error.proto)

| Enums ||
|---|---|
| ## `FIELD_HAS_SUBFIELDS` | The field mask updated a field with subfields. Fields with subfields may be cleared, but not updated. To fix this, the field mask should select all the subfields of the invalid field. |
| ## `FIELD_MASK_MISSING` | The field mask must be provided for update operations. |
| ## `FIELD_MASK_NOT_ALLOWED` | The field mask must be empty for create and remove operations. |
| ## `FIELD_NOT_FOUND` | The field mask contained an invalid field. |
| ## `UNKNOWN` | The received error code is not known in this version. |
| ## `UNSPECIFIED` | Enum unspecified. |